Prospects for regeneration therapy with stem cells

Abstract

“Stem cells” is the general term for cells that have the ability to renew themselves and the ability to differentiate into the cells that compose tissues. Stem cells possess a combination of “pluripotentiality”, which is the source of their ability to differentiate into various cell types that compose tissues and to fulfill their functions, and “self-renewal” ability, which replenishes “stem cells” themselves in the undifferentiated state by cell division.
Stem cells or undifferentiated cells in vertebrates^1-4), are broadly classified into two types: stem cells in the embryo stage, and adult stem cells, which are present in the tissues of adults. When organs are formed during embryonic stage, organogenesis is achieved by vigorous renewal by embryonic stem (ES) cells, which have very high proliferative capacity, and by orderly differentiation of tissue cell groups (patterning)^1-4). ES cells are cells in the initial state when the fertilized egg is in the process of dividing, and since they harbor the ability to become any stem cells required for embryonic tissue-patterning, they are also called pluripotent stem cells. Induced pluripotent stem cells (iPS cells)^{5, 6)} are artificially produced stem cells that are endowed with the same pluripotency to differentiate as these ES cells. In theory, cells that possess this pluripotency are able to differentiate into the constituent cells of every organ and tissue in the body. Therefore transplantation-based therapeutic application by using autologous cells as the source of production of iPS cells came closer to becoming a reality. Furthermore, established iPS cells from various diseases can also provide human stem cell resources for pharmacological, diagnostic or genetic evaluation.